What is the normal function of the KLKB1 gene?

The KLKB1 gene provides instructions for making a protein called prekallikrein. Prekallikrein is produced in the liver and circulates in the blood. A molecule called factor XII converts prekallikrein to another protein called plasma kallikrein, and plasma kallikrein helps turn on (activate) more factor XII. Plasma kallikrein and factor XII are involved in the early stages of blood clotting as part of a process called the intrinsic coagulation pathway (also called the contact activation pathway). Blood clots protect the body after an injury by sealing off damaged blood vessels and preventing further blood loss.

The interaction between plasma kallikrein and factor XII also initiates a series of chemical reactions resulting in the release of a protein called bradykinin. Bradykinin promotes inflammation by increasing the permeability of blood vessel walls, allowing more fluids to leak into body tissues. This leakage causes the swelling that accompanies inflammation.

Does the KLKB1 gene share characteristics with other genes?

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? in the Handbook.

How are changes in the KLKB1 gene related to health conditions?

At least nine KLKB1 gene mutations have been identified in people with a blood condition called prekallikrein deficiency, which does not generally cause any health problems. The condition is usually discovered when blood tests are done for other reasons.

The KLKB1 gene mutations that cause this condition reduce or eliminate functional plasma kallikrein in the blood of affected individuals and likely impair the intrinsic coagulation pathway. Researchers suggest that this lack (deficiency) of functional plasma kallikrein protein does not generally cause any symptoms because another process called the extrinsic coagulation pathway (also known as the tissue factor pathway) can compensate for the impaired intrinsic coagulation pathway. Either pathway can activate proteins that are needed later in the clotting process.

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